Messaging, Information and Media Sector
Radio Research Laboratory
From Standard WLAN’s
to Wireless ATM
Technology for Multimedia Communications
The Second IEEE Workshop on Wireless Local Area Networks
Worcester Polytechnic Institute, October 24-25, 1996
Paul Odlyzko
Motorola MIMS, Radio Research Lab
50 E. Commerce Drive
Suite M1
Schaumburg, IL 60173
paul_odlyzko@wes.mot.com
10/25/96
From Wireless LAN’s to Wireless ATM
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Messaging, Information and Media Sector
Radio Research Laboratory
Outline
• What is a “standard WLAN”?
• Performance goals and expectations
• Architectures and applications
- from LAN to Multimedia and Wireless ATM
• Market perspective
• Regulatory issues - unlicensed spectrum in US and Europe
• Products and technology demonstrators - proprietary solutions, standards
initiatives and EC-sponsored projects
• HIPERLAN and 802.11
• Quality-of-Service concerns
• Propagation environment - power, attenuation and multipath
• Wireless ATM in the NII/SUPERNet band
• Simple Asynchronous Multiple Access as etiquette and protocol
10/25/96
From Wireless LAN’s to Wireless ATM
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Messaging, Information and Media Sector
Radio Research Laboratory
What is a “standard WLAN”?
Infrared - history and IrDA (Infrared Data Association), laser links outdoors
• ISM - FCC Part 15 Spread spectrum 902-928; 2400-2483; 5725-5825
– 1 watt, mandatory spreading
– secondary use, must accept interference
– Part 15.249 unrestricted for EIRP below .75 mW
– “Garbage band” problems - rules practically unenforceable
– need for robustness, survival
• WinData duplex ISM Ethernet 2.4 GHz and 5.7 GHz, wire replacement
concepts rather than mobility
• 900 MHz WaveLAN from NCR, Proxim, Xircom and others
2.4 GHz systems - proprietary as well as 802.11 1997?),
advertised 2 Mbps for direct sequence or hopper or hybrid possible
10/25/96
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Messaging, Information and Media Sector
Radio Research Laboratory
What is a “standard WLAN”? (cont’d)
• “Narrow band” licensed and unlicensed
–
–
–
–
Motorola-Codex project, spectrum not allocated
Altair in 1990, wire replacement concepts rather than mobility,
Olivetti wireless LAN based on DECT
DECT branch formed in 1991 for wireless LAN leading to RES10,
5.150 GHz to 5.3 GHz, 17.1 to 17.3 GHz
• New unlicensed spectrum
– WINForum for 2 GHz
– WINForum for 5 GHz
– mmWave Etiquette Group for 60 GHz
10/25/96
UPCS
NII/SuperNet
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Messaging, Information and Media Sector
Radio Research Laboratory
Performance goals and expectations
• Coexistence with wireline LANs - interfacing with competition
• Ethernet 802.3
–
–
–
–
25 Mbps ATM
30 Mbps cable (asymmetric?)
100 Mbps
Gigabit movement
• Sidelined wired LANs
• Data rate
– ISM
– narrowband
• Wireless ATM
– RES10 talks about 50,000 ATM cells per second
10/25/96
From Wireless LAN’s to Wireless ATM
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Messaging, Information and Media Sector
Radio Research Laboratory
Architectures and applications from LAN to Multimedia and Wireless ATM
• Packet radio, half-duplex (TDD),
• Hand-over and forwarding (HIPERLAN)
• Perceived cost of infrastructure
• Centralized control (“access point”)
– Altair, IEEE 802.11 (BSS)
• Peer-to-peer
– WaveLAN, HIPERLAN (“Type 1”)
• Point-to-point, point-to-multipoint
10/25/96
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Messaging, Information and Media Sector
Radio Research Laboratory
Market perspective
• Hope for “horizontal”
– Metricom (wide-area network)
• Limited “vertical” markets so far
– computer maintenance (ARDIS - really a WAN) - ,
– point of sale applications warehouses, fleet management
– hence proprietary approaches are doing fine
• What limits commercial success so far?
commonly advanced explanations:
–
–
–
–
10/25/96
price, range,
low speed,
limited functionality,
no “killer apps”
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Messaging, Information and Media Sector
Radio Research Laboratory
Market perspective - cont’d
• Conjectures on how the wireless LAN market will develop:
–
–
–
–
access to Internet
multimedia notebook computers
will PDAs take off?
returning motivation: cable replacement, this time for portables Open Office
– tetherless nomadicity rather than fully mobile multimegabit
communications
• Expectations of the market:
– plug-and-play for RF naive, misguided, ignorant or just oblivious
users – higher expectations in-building than outdoors
• Will there ever be the “year of the Wireless LAN”?
– It will take a few years just as LAN networking
10/25/96
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Messaging, Information and Media Sector
Radio Research Laboratory
Regulatory issues
• World Radio Congress;
• Unlicensed spectrum in US and Europe;
• FCC and CEPT;
• coexistence with terrestrial microwave and satellite
communications
• UPCS
– for 1910-1930 one end needs to be tied - until microwave users are
relocated, hence suitable only for wireless PBX or such
– 2390 same spectrum etiquette as 1910-1920
– coexistence for non-interoperable systems
• 5 GHz first chance for world-wide market
10/25/96
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Messaging, Information and Media Sector
Radio Research Laboratory
Products and technology demonstrators
- proprietary solutions, standards initiatives
• “Mature” products:
– 900 ISM proprietary systems
– 2400 ISM proprietary systems
– Proxim initiative (open air interface as an alternative to 802.11)
• Standards-oriented developments
• European projects:
–
–
–
–
–
10/25/96
LAURA
pre-HIPERLAN test bed
HIPERION
feasibility of HIPERLAN
Magic Wand Wireless ATM
ACTS
MEDIAN
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Messaging, Information and Media Sector
Radio Research Laboratory
HIPERLAN
ETSI RES10, 5.15-5.3 GHz, 17.1-17.3 GHz
• Motivation: faster is better
• Process:
– Transmission Techniques Group (TTG)
– Control Techniques Group (CTG)
– Consensus
• 5 channels in 5 GHz
– 5176.468 MHz lowest center frequency
– 23.5294 MHz separation
– 10 ppm
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Messaging, Information and Media Sector
Radio Research Laboratory
HIPERLAN
equipment classes
Table 28: Permissible combinations of transmitter and receiver classes
Transmitter class Transmitter class Transmitter class
A (+ 10 dBm)
B (+ 20 dBm)
C
(+ 30 dBm)
Receiver
class A
Permissible
Not permissible
Not permissible
(- 50 dBm)
Receiver
class B
Permissible
Permissible
Not permissible
(- 60 dBm)
Receiver
class C
Permissible
Permissible
Permissible
(- 70 dBm)
NOTE:
The figures in parentheses indicate the nominal transmitted power
(EIRPEP)or receiver sensitivity associated with each class.
10/25/96
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Messaging, Information and Media Sector
Radio Research Laboratory
HIPERLAN
• Data burst structure
–
–
–
–
High-bit-rate training sequence (450 bits GMSK at 23,529 4 Mbps)
Low-bit-rate header (FSK at 1.4706 Mbps or 1:16)
High-bit-rate data (GMSK)
47 or fewer blocks of 496 (416 net) bits per packet
• CSMA - Non-Pre-Emptive Priority Multiple Access (NPMA)
– immediate access if sensed idle for 1700 bit times
– channel access resolution otherwise
» prioritization
» elimination
» yield
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From Wireless LAN’s to Wireless ATM
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Messaging, Information and Media Sector
Radio Research Laboratory
HIPERLAN
• Quality-of-Service provisions
– “Best effort” basis
– Priority
– Packet lifetime
• Uni-cast and multi-cast
• Path discovery and forwarding
• Power saving provisions
– scheduling for p-saver and p-supporter
– LBR header
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Messaging, Information and Media Sector
Radio Research Laboratory
IEEE 802.11
standard for 2400 to 2483.5 MHz
(2471 to 2497 in Japan)
• Physical layer
–
–
–
Frequency hopper (FH)
Direct sequence (DS)
Infrared (IR)
79 hopping frequencies (23 in Japan)
processing gain of 11
• SCMA/CA channel access
• Hopping pattern selection
– sets of 26 hopping patterns
• Spreading signal
– 11 center frequencies defined (US)
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Messaging, Information and Media Sector
Radio Research Laboratory
IEEE 802.11
•
•
•
•
Power management
Narrowband interferers
Microwave ovens
Quality-of-Service concept
–
–
–
–
Bandwidth guarantee
Data integrity
Delay
Delay variance
• Quality-of-Service provisions
– Time-bounded services
– Hidden-node effect mitigation
10/25/96
From Wireless LAN’s to Wireless ATM
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Messaging, Information and Media Sector
Radio Research Laboratory
Quality-of-Service Concerns
• Data integrity
– ARQ
– FEC
• Time-bounded services
– Real-time voice
– Video
– Audio
• Latency
• Latency variance
• Will “Standard WLAN’s” work?
– Reservations re throughput with short packets
– Long packet increase “jitter”
10/25/96
From Wireless LAN’s to Wireless ATM
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Messaging, Information and Media Sector
Radio Research Laboratory
Propagation environment
power, attenuation and multipath
• Inverse relationship between distance and data rate
• Power constraints
• Antenna gain constraints- definitions
• Models of attenuation indoors
– exponent 3 to 4
– free space and walls
• Optical analogy increasingly applicable with higher
frequencies
10/25/96
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Messaging, Information and Media Sector
Radio Research Laboratory
WATM for NII/SUPERNet
5.100-5.350 and 5.725-5.875 GHz
• Proposals from WINForum and Apple not restrictive
• Notice of Proposed Rule Making FCC 96-193 opens
dialogue
• Spectrum sharing etiquette expectations:
– enabling high QoS systems
– flexibility for multi-media communications
• Need for alternatives to support Wireless ATM
– ATM cell: the byte of the 90’s
– individual ATM cells
– trains of ATM cells
10/25/96
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Messaging, Information and Media Sector
Radio Research Laboratory
Assumptions
• A radio channel is most efficiently shared among users
with CBR requirements.
• Over any sufficiently short period of time (Tc), any
bandwidth requirement is CBR.
• The practical lower limit to Tc is the amount of time
and overhead required to re-acquire bandwidth.
• Statistical multiplexing, within a multi-service device,
increases Tc.
• Multi-Media devices will require protocols that
support both infrastructure based (centrally controlled)
and non-infrastructure based (ad-hoc) networks.
10/25/96
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Messaging, Information and Media Sector
Radio Research Laboratory
Desired Qualities
•
•
•
•
Provide a simple bandwidth setup mechanism
Support for devices with widely varying bit rates
Reduce the number of “collisions”
Support the development of both ad-hoc and centrally
controlled protocols.
10/25/96
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Messaging, Information and Media Sector
Radio Research Laboratory
Simple Asynchronous Multiple Access
(SAMA)
Probe Cell
Ack
Data
Data
Frame length
• There is no “bandwidth set up” phase.
• Every unit observes the same frame size.
• Each transmission burst is divided into cells of the
same time duration.
10/25/96
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Messaging, Information and Media Sector
Radio Research Laboratory
Probing for Channel Access
Unit A
Probe Ack Data Data Data Data Data Data Data
Unit B
Probe
FEC
FEC
FEC
Probe Ack Data Data Data Data
Units A + B
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Messaging, Information and Media Sector
Radio Research Laboratory
SAMA
Ad-Hoc Networking
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Messaging, Information and Media Sector
Radio Research Laboratory
SAMA
Centrally Controlled Network
Multi-Frame controlled
by the Base Station
Base Station
CP
CP
Wired Infrastructure
CP
Control
Packet
Data
Packet
Data
Packet
Data
Packet
Control
Packet
Data
Packet
Data
Packet
Data
Packet
CP
CP
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Messaging, Information and Media Sector
Radio Research Laboratory
RF Fading Environment
10/25/96
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Messaging, Information and Media Sector
Radio Research Laboratory
Fading Patterns
Omni vs. Directional Antenna
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Messaging, Information and Media Sector
Radio Research Laboratory
Effect of Switching Antenna on
Fading
(Short packets will get through more often)
10/25/96
From Wireless LAN’s to Wireless ATM
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Messaging, Information and Media Sector
Radio Research Laboratory
Omni Antenna
Received Signal Strength
10/25/96
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Messaging, Information and Media Sector
Radio Research Laboratory
Directional Antenna
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